Characterization and expression analysis of a thaumatin-like protein PpTLP1 from ground cherry Physalis pubescens

Ground cherry, Physalis pubescens, is mainly cultivated as a fruit worldwide and popularly used as a food supplement and traditional Chinese medicine. Plants are challenged by external environmental stress and can initiate resistance to the stress through the regulation of pathogenesis-related (PR) proteins. Among PR proteins, PR-5, a thaumatin-like protein (TLP), was identified in many plants and found to be able to enhance stress resistance. However, PR-5 in ground cherry is not characterized and its expression is yet to be understood. In this study, a PR-5 protein PpTLP1 in P. pubescens was firstly identified. Analysis of the amino acid sequences revealed that PpTLP1 was highly similar to PR-NP24 identified in tomato with a difference in only one amino acid. Expression analysis indicated that the PpTLP1 gene was highly expressed in leaf while the PpTLP1 protein was tissue-specifically accumulated in cherry exocarp. Furthermore, the down-regulation of PpTLP1 in ground cherry was induced by NaCl treatment while the up-regulation was promoted by the infection of Sclerotinia sclerotiorum and Botrytis cinerea. This study will provide a new plant resource containing a TLP in Physalis genus and a novel insight for the improvement of postharvest management of ground cherry and other Solanaceae plants.